The invention relates to an optical sensor.
An optical sensor of this type is known from German patent document DE 199 17 509 C1. The optical sensor is used for detecting objects in a monitoring range and comprises a distance sensor with a transmitter for transmitting light rays and a receiver for receiving light rays, an evaluation unit for evaluating the signals received at the receiver and a deflection unit on which the transmitted light rays are deflected so that these periodically sweep across the monitoring range.
The dimensions of different safety zones, forming defined partial areas of the monitoring range, are stored in the evaluation unit of the optical sensor. However, the object detection does not occur in the complete monitoring range, but in a selected safety zone. For the safety zone selection, several switches are connected via respectively one feed line to an evaluation unit input, wherein each input is assigned a stored safety zone. Upon activation of a switch, a predetermined signal value is present at the assigned input which corresponds to an activation of this input. The safety zone assigned to this input is also activated along with the input, thus making it possible to detect the objects in this safety zone. For testing purposes, respectively one signal value is transmitted via an evaluation unit output to the feed lines. If no errors occur, this signal is then waiting at the respective evaluation unit input.
One essential advantage of this arrangement is that an error-safe selection of a specific safety zone can be made via a single input of the evaluation unit. The protection against errors in this case is ensured through emitting the signal values at the evaluation output, which are read back into and checked in the evaluation unit via the inputs.
An optical sensor of this type, however, has the disadvantage that a plurality of separate inputs must be provided for activating these safety zones, in particular for a higher number of stored safety zones In addition, this results in an undesirably high cabling expenditure for connecting the individual inputs of the optical sensor.
German patent document DE 195 23 843 C1 relates to a method for detecting objects in a monitoring range. According to this method, at least a first monitoring device is installed at the edge of an operating area, with the monitoring range positioned parallel to a plane for a driving lane within the operating area and a second monitoring device is arranged at an access ramp to the operating area which monitors a second monitoring range, positioned in a plane perpendicular to the operating area.
A reference object moving along a track is surveyed with the second monitoring range. From these measuring values, the contour edges of the range monitored by the first monitoring device is derived.
German patent document DE 44 05 376 C1 relates to a method for detecting objects located inside a monitoring range or objects penetrating this range, wherein a device having at least one transmitter, at least one receiver and an evaluation unit are used for the monitoring. A transmitting beam emitted by the transmitter transverse to the beam direction of the transmitter is guided inside the range. For different orientations of the transmitted beam, the distance between the device and the object are determined and the position measuring values are stored in the evaluation unit.
To detect objects having a specific contour, the position measuring values for the respective object are compared to desired values, which are computed in the evaluation unit from the object contour at a predetermined position in the range to be monitored. An object having the specific contour is considered detected if a minimum number N of the position measuring values drops by the desired values within at least one tolerance band T. The minimum number N of the position values and the dimensioning of the tolerance band T are selected in the evaluation unit in dependence on the position measuring values scattering.
German patent document DE 197 21 105 A1 relates to an opto-electronic sensor arrangement with a light transmitter for transmitting a light bundle to a monitoring range, a light receiver for receiving a light bundle, formed by transmitting light that is reflected by an object located in the monitoring range in the direction of the light receiver, wherein the receiving light bundle is at a changeable beam angle to the transmitting light bundle in dependence on the distance between the object and the sensor. The opto-electronic sensor arrangement further includes a control and evaluation unit for processing the output signal from the light receiver. The light receiver is provided with a multi-element light sensor comprising at least four individual sensing elements, which are arranged adjacent to each other, such that the receiving light bundle hits different sensing elements in dependence on the beam angle.
With a network of switches, sums and/or differences of the output signals of the multi-element light sensor can be formed in different ways.
German patent document DE 100 01 017 A1 relates to a reflex light scanner for detecting an object in a monitoring field, comprising at least one light transmitter, at least n>2 photodiodes, a transmitting optic, a receiving optic and an evaluation unit, wherein the photodiodes are interconnected to form a photodiode line and are parallel connected relative to each other.
The switching distance can be adjusted particularly easy and fast owing to the fact that the photodiodes are connected on the one hand to a joint potential and that adjacent photodiodes are, on the other hand, respectively connected to each other via an opener, that n−1 openers are provided for n photodiodes and that the first photodiode is connected to a first channel of the evaluation unit and the nth photodiode is connected to a second channel of the evaluation unit.
European patent document EP 0571 913 B1 relates to a system for recording optical targets. To detect the optical targets, patterns are defined within the picture to be evaluated, which are respectively correlated with parts of the picture in a correlating device. The selection of the patterns occurs via an evaluation unit and in dependence on specific picture features.
European patent document EP 0571 892 B1 relates to an image-detection system for detecting the images of labels. This system is provided with two target processing units by means of which target detection signals are generated. These units are connected to a detection device for adjusting the generated target detection signals. Finally, the orientation of the label image is determined in an additional processing unit.